Military protractor



HNLLMTFL Feb. 28, 1928.

Y v Patented Feb. 28, 19208.

UN'ITED'ST-S HARRY A. Musnarnor" e 1 -Ireneo, Inrinis. 'j

minimaler riaorinfiernos. i

" Rf'iiea for abandoneiiappiieanonserial No. zassaiiidfneember 19, 1925. This application andv i i f i .'August29,1927. Serial No.`216,184, l Y g.

This invention relates yto an improved measuring instrument, and it has morepan` ticular reference `to a military protractor for use in military science in 'reading maps, lay- 5 ing out and measuring angles, and laying oft angles forthe degree and mil system of circular measurements." i

The lpresent application is a substitute' for an application identilied` by Serial No.

` l 74,336,1`iled by me under dateof December 9,1925, now abandoned. v .i

'Briefly described', the alleged`A novelty f herein embodied is Lbased u pon an instrument of this classl whiclrcomprises a rectangularf sheet of appropriate Vmaterial,

formed witha slot which runs parallel to one longitudinal'edge, this slot constituting the'basefline of 'a protractor and being formed vwith a centrally located verter` Also'located on the sheet and disposed in sp'ac'edfparallelism to the first named s lot is'a second longitudinal slot. Cooperating with these two longitudinal slots, we find' a pair of relatively short vertical end slotsV whose opposite ends 5 extend beyond and thereby overlap the end portions of the first named slots. second named longitudinal slot and the end slots are formed with individual scale lines radiating from the vertexand arranged on the overlapping end portions of the ,end slots in such a manner as to provide for continuity' of measurement.

In the drawing Y The single figure represents atop plan view of an instrument constructed in accordance with the present invention.

' Referring now toy the drawings Aby refer` ence numerals it will be observed thattlie end slots, being disposed somewhat closek to the top edge of the sheet. Disposed in spaced parallelism with the slot 4 is a bottom slot 5 having a vvertex 8 formed'cen- The opposite edges of the reference vcharacter 1 designates generallyv ous as for 'instance at 30 degrees.y

trally on the Ainner edge thereof. vAlong the inner edges of. slots`2, 3",andi4 placed scalelof degreesrepresentedby the reference numeral 8.11` This scale runs from 0 degrees onthei'ight to 180-degrees on` the left; Alsoitfruns vfrom v180 degrees-on the righti'to 360 degrees on theuleft. v.Along the --ou'teredgesef slots2, 3 and 4 is placedascale: of angular nieasurementin mils, de s-y ignated V by the reference charactersand starting from ,0. mils' fromA the rightzand continuing nto' 3200 mils on the left,and from f 6400 mils right.VV V:,At this fact that the Vscales for angular measurement usedjin -inilitary terms are -madeon two 'system isdivided into V360 degrees,each degree being divided into 'minutes, and each minnte being divided into 60 seconds. Secondly,

ion "the left-.to 3200 inilsonfthp i bint atientionisinnted-to vthe tenis. "First, lthe degree. systeiirwvliere `sys- Y c l there is the mil system where the circumfer ence is divided into 6400 equal parts called mils.V A mil is theangle subtended'by an arc of one foot at a distance of 1000 feet. Incidentally the .figure 6400 is. a practical ure adopted by the army instead of 6283.2, the actual number of mils in a circumference.

As before stated the particular advantage of this arrangement of individual scales is to provide for continuity of'measurements so that there Vwill be no break in the scale. Hence the'ov'erlap is sufficient to provide for saV the scales'of degrees of vmils being continuous to this extent. gree graduation is found inthe inner edge of slot'2 and on theinner edge of slot 3 also.y In reading' or laying off angles the user For instance, the 30 def starts at 0 degrees or 0. mils as the case may be from the right, reads up the scales on the slot 2 as far asthey go, then locates the slotv 2 and slot 3, reads along slot 3 and down onV slot .4, locating as before the last reading of slot 3 on slot 4. It is thus seen that continuityv of angular-fmeasurement is provided.

`Gf course the' widths of'slots 2` 3,' 4 and 5 is not definitely specified but willlbe such as to make for convenient use of the scale and markingy of the pencil on either edge of the slots.,V .f

Attention is also invited to the fact that the A155 2 l M` A 1,660,624

i horizontal slot is used, from 1.5() degrees to v180 vdegrees the vleft hand slot is usedy for measuring and plotting angles in degrees.

If the angles `are desired in mils then the mils scales are used. This placing of theI mils lof angular measurement f around an arrangefY i ment of slots permits placing of more than one direct readingqand sliding the Yscale of angular measurement on a protractor. The

' Vof angular measurement thatcan be usedjv ordinary protraetor can only have one scale directly for reading and plotting the scale of angular measurement on a protractor. v By direct reading is meant, reading the angle by means of-a scale, the division pointsofwhich can be `marked with a pencil or Ya pointer.

More tlianone scale can be placed onV the ordinaryprotractor, but notdirect reading.

' If morelthan .one scale is used,lftli'enf onev Vmight vbe fitted inside the edges, division points cannot be marked by pencil.v

By arrangingvtlie scales herein shown in.

i spaced relation to the marginal edges of the sheet, suicient space is leit for dispositionV of coordinate rules.A For example, coordi-A nate ruler forja grid, interval of 1000 yards A and a map scale of 1 to 20,000 is shownatfl merely to illustrate this featureof the invention. l

From the foregoing descriptionand drawe ing it Will be seen that I have produced an exceptionally original measuring instrument for military purposes Which is characterized by the presence Yof cooperating overlapping slots having individual scale` measurements on their opposite edges so located as to pro'- v ments.

fore amore'lengthyl description is believed unnecessary, p f y i Minor changes in the sliapesize, and rearrangementiof vfeatures mayV bepres'orted to Y Within theyscopeof the adjoined claim.V

Having .thus described the inventiou., Wliat I claim as new is :e 1 v Y A measuringdevice of the kclass described comprising a rectangular lsheet formed with a slotr running parallel to one longitudinal edge. and having its inner ledge forming the baseline of aprotractor, said inner edge having marked thereon a vertex, second'longitudinal` slot,and a ypair ofV transverse slots,

spaced outwardly from ,the endsof the longi`V tudinal slots andextending fromv the first longitudinal slotte points beyond the second Aslot and perpendicularly thereto, the edges of the second longitudinal and transverse l slots being provided with graduationvlines radiating from said vertex as aV center, some of the lines Vattlie ends of the second longitudinal slot being .duplicated .on the tranS- s verse lslots to provide continuity of measure-v ments.

Y In ,testimony whereof I'aiix my signature.

instaura. MUSHAM.; y 

